A family of devices exists that are designed to be lowered into exploratory boreholes, which are typically 3 inches diameter, to ascertain soil and/or rock modulus properties of the soil and/or rock surrounding the exploratory borehole. These exploratory boreholes can be larger or smaller than 3 inches (76 mm), but are generally not greater than 6 inches (152 mm). Examples of such devices designed to be lowered into exploratory boreholes include:
the Goodman Jack (U.S. Pat. No. 3,446,062) and derivatives (e.g., U.S. Pat. No. 3,961,524), which are lowered into an exploratory borehole to measure the modulus of soil and/or rock by application of two forces in two opposing directions;
flat-plate dilatometers (e.g., U.S. Pat. No. 4,043,186), and derivatives (e.g., U.S. Pat. No. 8,776,583), which are first pushed into a soil mass and then activated, in order to measure the modulus of soil in one direction by transverse inflation of a flat, flexible membrane; and
pressure meters, which are lowered into an exploratory borehole to measure the modulus of soil and/or rock by radial expansion of an inflatable chamber.
These devices designed to be lowered into exploratory boreholes typically embody two primary characteristics. First, the devices are relatively small in cross-sectional dimension, i.e., typically less than 3 inches (76 mm), in order to fit into a standard-size exploratory borehole, i.e., 3 inches (76 mm). Second, the active maximum displacement of such devices into the soil and/or rock is minimal, e.g., typically fractions of an inch. Therefore, these devices are effective in ascertaining either elastic modulus (pounds per square inch) or bulk modulus (pounds per cubic inch) of the surrounding soil and/or rock, within a small stress field. Modulus, such as elastic modulus and bulk modulus, is a property of material typically ascertained at very small deformations of the material.
A sacrificial split-lateral test was first described by O'Neill and Majano (1995). Split-lateral testing using a sacrificial hydraulic O-cell jack, such as a sacrificial hydraulic O-cell jack cast into a drilled shaft element has been performed on several projects in North America. Brown and Camp (2000) used assemblies with two sacrificial (O-Cell™) jacks each. Additionally, Kahne and Brown (2002) used a system with a retrievable hydraulic (O-Cell™) jack, positioned in an access way cast into the shaft, but the hydraulic jack was able to load the shaft at only one location. These innovations, though commercially available for 20 years, were never patented.
U.S. Pat. No. 4,461,171 is directed to a device to determine the in-situ deformability of rock mass.